My understanding was that the most 12v pumps weren't made for the short cycling every time I trigger the wand. I had a drum w/ pump on it many years ago but the pump kept burning up. Hence the bladder/balloon which fills upand supplies water allowing the pump to run a gallon or so at a time. Unfortunately the bladder is like $350 so a pump that can short cycle would be cheaper and simpler.
Using the suction from the cat pump would be ideal but the machines I had that did this (
butler/WM pto) had the pump at floor level. My machine has the pump near the van roof so it would be alot of uphill distance and I was concerned about starving the pump.